[Determination of feprazone and one of its metabolites in human plasma after high-performance liquid chromatographic or thin-layer chromatographic separation].

Two procedures suitable for pharmacokinetic routine analysis are described for the simultaneous determination of feprazone and one of its metabolites (DA 3505) in plasma samples. After extraction from acidified plasma feprazone and DA 3505 are determined by measuring UV absorbance after thin-layer chromatographic (TLC) separation (reversed-phase TLC plates; methanol--water--formic acid) or high-performance liquid chromatographic (HPLC) separation (silica gel column; hexane--tetrahydrofuran--acetic acid). Limits of detection are 0.1 microgram feprazone per ml plasma and 0.2 microgram of its metabolite per ml plasma using the HPLC method. Concentration down to about 0.5 microgram/ml plasma of both compounds can be determined using the TLC method.